Drill and method for producing a drill

ABSTRACT

The invention relates to a drill comprising a body which extends along a longitudinal axis (L) from a rear side (B) to a front side (F), wherein the body comprises a main cutting edge on the front side (F), wherein the body comprises at least one guide bevel which extends in axial direction (A) and toward the front side (F), wherein, toward the front side (F), the guide bevel has an end section which is tapered. The invention further relates to a method for producing such a drill.

RELATED APPLICATION DATA

The present application claims priority pursuant to 35 U.S.C. § 119(a)to German Patent Application Number 102019211827.5 filed Aug. 7, 2019which is incorporated herein by reference in its entirety.

FIELD

The invention relates to a drill and a method for producing a drill.

BACKGROUND

Drills are rotary tools and are used for machining a workpiece. Whendrilling a bore in the workpiece using the drill, the drill is subjectedto high loads. The so-called cutting corner, which is located at thetransition from a main cutting edge on the front side of the drill to alateral guide bevel, is particularly affected. The cutting corner andthe guide bevel in this area wear down over time, which, in unfavorablecases, further increases the load, so that the wear and also the risk ofparts of the drill breaking off escalates.

SUMMARY

With this in mind, the object of the invention is to provide an improveddrill. This drill should in particular exhibit reduced wear and shouldalso, in particular even in the case of progressive wear, allow the bestpossible machining of a workpiece. A method for producing such a drillis to be provided as well.

The object is achieved according to the invention by a drill having thefeatures according to claim 1. Advantageous configurations, furtherdevelopments, and variants are the subject matter of the subclaims. Thestatements made in connection with the drill apply analogously to themethod and vice versa.

In general, the drill is used for machining a workpiece, in particularfor drilling a bore in a workpiece. The drill comprises an in particularelongated body, which extends along a longitudinal axis from a rear sideto a front side. On the rear side, the drill in particular comprises ashaft for mounting in a tool mount. On the front side, the drillcomprises a tool tip for machining the workpiece. On the front side, thebody comprises a main cutting edge, which is in particular part of thetool tip and which engages on the workpiece during operation.

The body further comprises at least one guide bevel, which extends inaxial direction and toward the front side. The axial direction isparallel to the longitudinal axis. The guide bevel is preferablyspiral-shaped and then extends helically around the longitudinal axis. Astraight guide bevel is conceivable as well, however, and also suitable.The guide bevel is disposed on a lateral outer surface of the drill andis used to guide the drill in the bore during operation. For thispurpose, the guide bevel lies against and extends along an inner wall ofthe bore, which results in a corresponding mechanical stress. The guidebevel is thus in particular the part of the body that, during operation,is in contact with the inner wall of the bore in radial direction, i.e.laterally. The rest of the body of the drill, and specifically its outersurface, is set back in radial direction, i.e. perpendicular to thelongitudinal axis, in relation to the guide bevel. In other words, theguide bevel protrudes in radial direction with respect to the outersurface. The guide bevel thus determines a maximum diameter of thedrill, which otherwise, i.e. along the outer surface, then has a smallerdiameter. Viewed in the direction of rotation, the guide bevelpreferably precedes the outer surface. The guide bevel thereby inparticular separates the outer surface from a flute in the body. Alsoconceivable and equally suitable are configurations in which the guidebevel follows the outer surface or divides said surface into multiplepartial outer surfaces in the direction of rotation. The guide bevelfurther in particular comprises a so-called secondary cutting edge,which precedes in the direction of rotation and thus forms a leadingedge of the guide bevel.

In the present case, the guide bevel has an end section toward the frontside, which is tapered. In other words: The guide bevel extends towardthe front side and, in the direction to the front side, ends in an endsection which is tapered in relation to the rest of the guide bevel. Theend section forms an end of the guide bevel. The guide bevel thus has areduced bevel width at the end toward the front side. The bevel width ofthe guide bevel is preferably measured perpendicular to the guide bevel.

One advantage of the invention is in particular that the drill wearsless due to the guide bevel being tapered at the end. This is inparticular based on the observation that the guide bevel, which precedesin the direction of rotation, is particularly heavily stressed andtherefore initially wears predominantly in the region of the secondarycutting edge and the cutting corner. As soon as these leading sectionsare at least partially worn off, the sections of the guide bevel behindthem are correspondingly stressed by pressure and friction and wear downas well, as a result of which there is still the danger that parts ofthe body can come loose or be knocked off. One basic idea of theinvention is therefore in particular to omit or reduce these trailingsections or parts of the guide bevel from the outset, so that they arenot stressed by pressure and friction when the guide bevel starts towear and then further impair the operation of the drill. As a result,optimum machining of the workpiece remains possible over a remarkablylong period of time. The service life of the drill is moreoveradvantageously extended as well.

A guide bevel with a tapered end section is particularly useful for adrill having a body which tapers toward the rear side, i.e. which has aso-called “taper”. Such a body is usually slightly cone-shaped, so thatits diameter on the front side is 1% to 5% larger, for example, and theguide bevel is therefore also particularly heavily stressed at thefront. However, a tapered end section is furthermore also generallyadvantageous for other drills.

The end section is preferably tapered by the formation of a free surfaceon the side of the body along the guide bevel. The body therefore has afree surface, which is disposed laterally and in particular replaces apart of the guide bevel so that it is narrower toward its end. The freesurface thus replaces a part of the guide bevel and is set back inradial direction in relation to said guide bevel. On the end section,the free surface and the guide bevel extend directly next to one anotherin axial direction, i.e. they are directly adjacent to one another. Thefree surface distinguishes itself from the guide bevel in that the drillhas a smaller diameter on the free surface. In operation, in particularonly the guide bevel is in contact with the inner wall of the bore, butnot the free surface. In this way, the contact surface of the drill tothe bore along the end section is reduced compared to a guide bevel witha non-tapered end section.

The free surface is thus similar to the outer surface, which is likewiseset back in radial direction relative to the guide bevel. However, atleast on the side of the body, the free surface is in particularsignificantly smaller than the outer surface. The free surface isseparate from the outer surface and is not a part of said outer surface,but the free surface preferably adjoins the outer surface. Whereas theouter surface typically extends along the entire guide bevel, the freesurface extends in axial direction only along a part of the guide bevel,namely along the end section, and therefore does not reach the rear sideof the drill. The outer surface is furthermore typically configured withan in particular constant radius, whereas the free surface does notnecessarily have a constant radius, but rather preferably deviates fromthat. In addition, the free surface protrudes in radial direction inparticular relative to the outer surface and is therefore locatedbetween the guide bevel and the outer surface with respect to theradius.

A configuration in which the free surface follows the end section in thedirection of rotation of the drill, in particular follows directly, isparticularly preferred. The guide bevel, and specifically in particularits secondary cutting edge, thus precede the free surface, so that theend section, which follows in the direction of rotation, transitionsinto the free surface which then slopes away in radial direction andthus results in a reduced diameter of the body behind the guide bevel.Lastly, following in the direction of rotation, the outer surface thenadjoins the free surface. In one configuration, a step is formed betweenthe free surface and the outer surface. In contrast, in anotherconfiguration, the free surface transitions to the outer surface withoutedges. All in all, viewed in the direction of rotation, there is anarrangement of the guide bevel, specifically its end section, the freesurface and lastly the outer surface, one behind the other.

The free surface preferably transitions into the guide bevel withoutsteps, i.e., in particular without edges. The free surface thusrepresents a surface that slopes away from the guide bevel, inparticular in the direction of the outer surface. There is then no stepor edge at the transition between the guide bevel and the free surface;instead the transition as a whole is continuous and rounded.

In one advantageous configuration, the free surface comprises twopartial surfaces, namely an axial surface which extends on the side ofthe body along the end section, i.e. predominantly in axial direction,and a radial surface which extends on the front side, i.e. predominantlyin radial direction, such that the free surface as a whole is curved,namely in particular from one side of the body toward the front side.This results in a further difference between the outer surface and thefree surface, such that the outer surface extends in axial directiononly up to a circumferential edge, thus ending at the tool tip, whereasthe free surface is inserted into the tool tip from the side of the bodyand beyond the circumferential edge. The two partial surfaces arepreferably both configured without edges and expediently also transitioninto one another without edges, so that the free surface is a curvedsurface that is entirely without edges. The tapered end section isformed on the side of the body by the axial surface. The radial surface,on the other hand, is disposed on the front side, generally points inaxial direction, and forms a part of the tool tip. In one suitableconfiguration, the free surface initially follows a generally conicalshape of the tool tip and, viewed from a center of the drill, thenslopes away in radial direction outward in a curved manner. In thecurved transition from the radial surface to the axial surface, the freesurface in particular has a radius of curvature that is preferablybetween 5% and 20% of a diameter of the drill, i.e. the drill diameter.

The radial surface preferably extends along the main cutting edge andfollows said edge in the direction of rotation. The free surface, moreprecisely its radial surface, is directly adjacent to the main cuttingedge and thus also determines a clearance angle of the main cuttingedge. The free surface extends in radial direction outward, inparticular to an outer end of the main cutting edge. In one suitableconfiguration, the free surface is a first free surface that extendsinward only along an outer part of the main cutting edge and to theinside adjoins a second free surface, which extends along an inner partof the main cutting edge and into the center. The second free surface isin particular larger than the first free surface. The first free surfaceis also referred to as the outer free surface, whereas the second freesurface is referred to as the inner free surface. The first and thesecond free surface together are also regarded as a single free surface;specifically in a preferred configuration in which the transitionbetween the first and the second free surface is continuous. To theinside, the free surface then extends to an inner end of the maincutting edge. In one suitable configuration, the inner end of the maincutting edge adjoins a chisel edge, which extends in the center of thedrill and is formed by a point thinning. Like the free surface, thepoint thinning is a forward-facing surface on the front side. To theinside, the point thinning preferably adjoins the free surface, inparticular directly.

The main cutting edge and the guide bevel, more specifically their endsection, suitably end together in a cutting corner that is adjoined bythe free surface which follows in the direction of rotation. The cuttingcorner thus in particular forms a respective end point for the maincutting edge and the secondary cutting edge. As a matter of principle,an imaginary boundary line between the guide bevel and the free surfacealso ends in the cutting corner. Overall, due to the taperedconfiguration, the guide bevel tapers in the direction toward thecutting corner and ends there. The cutting corner itself is entirelysurrounded by the guide bevel, the free surface which follows thecutting corner, and also in particular by a flute. The flute generallyin particular adjoins the main cutting edge and thus determines a rakeangle of said main cutting edge. In radial direction, the flute ispreferably delimited by the guide bevel, specifically by the secondarycutting edge.

The free surface is preferably configured entirely without edges, inparticular in the configuration with an axial surface and a radialsurface. A configuration is generally conceivable, in which the outersurface and the radial surface, i.e. a free surface that follows themain cutting edge, are separated by a circumferential edge that extendsin the direction of rotation around the longitudinal axis and ends inthe cutting corner. Due to the specific free surface, in which the axialsurface at least transitions into the radial surface without edges orwhich is even configured entirely without edges, the circumferentialedge ends prematurely and does not reach the cutting corner. In fact,the free surface separates the cutting corner from an end of thecircumferential edge and lies in between, so that a rounded andedge-free transition from the front side to the side of the body isrealized in the direction of rotation behind the cutting corner. Thefree surface can thus advantageously be produced in a single pass and ina single process step, and is preferably also produced in this manner.Proceeding from a semi-finished product having a circumferential edgethat extends to the cutting corner, the circumferential edge directlybehind the cutting corner is rounded by the free surface and, as aresult, in one suitable configuration, the cutting corner is moved aswell.

The guide bevel generally has a bevel width which, in the present case,varies due to the tapered end section along the guide bevel, i.e. issmaller on the end section. In a particularly useful configuration, thebevel width outside the end section corresponds to a normal width and,along the end section, the free surface has a width that together withthe bevel width of the end section corresponds to the normal width.Taken together, the free surface and the end section are thus just aswide as the rest of the guide bevel. The bevel width is preferablyconstant along the guide bevel outside the end section, so that theguide bevel has the normal width throughout, at least to the endsection, and the bevel width then deviates from the normal width onlyalong the end section. The difference to the normal width is filled inby the free surface.

Viewed from the side, the guide bevel is in particular strip-shaped, theend section in itself is strip-shaped as well, and likewise preferablyalso the free surface along the end section. More specifically, the freesurface and the end section are approximately needle-shaped orfunnel-shaped with a tapered section that is followed by a straightsection of constant width, which is then in turn followed by a furthertapered section that preferably ends in a point. The free surface,specifically its axial surface, and the end section extend parallel toone another, so to speak, at least along the straight sections, so thatthe free surface and the guide bevel quasi intertwine when viewed fromthe side. In other words: an imaginary dividing line between the endsection and the free surface extends parallel to the guide bevel, i.e.in the direction of said guide bevel. The width of the free surfacealong the end section is in particular constant or decreasing in thedirection toward the rear side, but not increasing. Conversely, thebevel width along the end section in the direction toward the front sideis likewise in particular constant or decreasing. There is therefore norenewed widening in the direction of the respective end. Instead, thewidth of the free surface and the bevel width preferably decreasemonotonically toward the respective end. The described parallel courseof the end section and the free surface is not mandatory and, in asuitable variant, an imaginary dividing line between the end section andthe free surface does not extend parallel to the guide bevel asdescribed above, but rather at an angle to it.

In one useful configuration, the free surface has a width along the endsection that is between 20% and 60% of a bevel width of the guide bevelalong the end section. The width and the bevel width are in particularmeasured on a respective straight section as described above.Particularly preferred is a width of 30% to 50% of the bevel width ofthe end section. The absolute width and the absolute bevel width dependon the specific configuration and dimensioning of the drill. Only as anexample, the normal width in one configuration is 2 mm, the bevel widththen tapers toward the end section to 1.3 mm, for example, before theguide bevel tapers further to the cutting corner. Correspondingly, thewidth of the free surface is then 0.7 mm.

In principle, it is possible and also suitable to form the free surfaceover the entire length of the guide bevel such that the end sectioncorresponds to the overall guide bevel. However, a configuration ispreferred, in which the end section is shorter than the overall guidebevel, i.e. only forms a part of said guide bevel. In one suitableconfiguration, the end section has a length that corresponds to 4% to40% of a diameter of the drill, whereby the length and the total lengthare measured along the guide bevel. In the case of a drill with a 20 mmdiameter, for example, the end section is then 0.8 mm to 8 mm long.However, the specific lengths depend on the actual dimensioning of thedrill.

To produce the drill, the end section is tapered by grinding the end ofthe guide bevel. This is in particular done using a grinding wheel.

Particularly preferred is a configuration, in which the end section istapered by grinding off a part of the guide bevel by grinding in a freesurface which extends continuously from the front side of the body to aside of the body. Proceeding from a semi-finished product having a guidebevel with an in particular continuously constant bevel width, the endof the guide bevel is partially removed and, as a result, the freesurface is formed. The free surface is preferably formed when grindingin an end face geometry of the drill, i.e. when grinding in the tooltip. The free surface is then expediently continued from the maincutting edge along the side of the body by inserting the grinding wheelinto the outer surface and the guide bevel, in particular in one steparound the circumferential edge, or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Design examples of the invention are explained in more detail in thefollowing with the aid of a drawing. The figures show, in each caseschematically:

FIG. 1 a drill in a perspective view,

FIG. 2 the drill of FIG. 1 in a front view,

FIG. 3 a section of the drill of FIG. 1 in a detail view,

FIG. 4 the drill of FIG. 1 in a different perspective view,

FIG. 5 the drill of FIG. 1 in a lateral view,

FIG. 6 the drill of FIG. 1 in a different lateral view,

FIG. 7 a variant of the drill of FIG. 1 in a perspective view,

FIG. 8 the drill of FIG. 7 in a lateral view,

FIG. 9 a further variant of the drill of FIG. 1 in a perspective view.

DETAILED DESCRIPTION

FIGS. 1 to 6 show sections of a first design example of the invention indifferent views. Each one shows a drill 2, which is used overall fordrilling a bore into a not depicted workpiece. The drill 2 comprises anelongated body 4, which extends along a longitudinal axis L from a rearside B to a front side F. On the rear side B, the drill 2 comprises anot depicted shaft for mounting in a tool mount. On the front side F,the drill 2 comprises a tool tip 6 and the body 4 further comprises atleast one, in this case two, main cutting edges 8 that are part of thetool tip 6. In FIGS. 7 and 8 , the drill 2 of FIGS. 1 to 6 is shown withadditional coolant channels that are not described in greater detail.FIG. 9 shows a further variant of the drill 2 in a perspective view.

The body 4 further comprises at least one guide bevel 10, which extendsin axial direction A and toward the front side F, wherein the axialdirection A extends parallel to the longitudinal axis L, i.e. inlongitudinal direction. In the design examples shown, the guide bevel 10is spiral-shaped and extends helically around the longitudinal axis L.The guide bevel 10 is disposed on a lateral outer surface 12 of thedrill 2 and is used to guide the drill 2 in the bore during operationand is thus the part of the body 4 that, during operation, is in contactwith the inner wall of the bore in radial direction R, i.e. laterallyand perpendicular to the longitudinal axis L. The rest of the body 4 ofthe drill 2, and specifically its outer surface 12, is set back inradial direction R relative to the guide bevel 10, as can be seen, forexample, in FIG. 1 .

In the design examples shown, the guide bevel 10 precedes the outersurface 12 when viewed in the direction of rotation U of the drill 2.The guide bevel 10 thereby separates the outer surface 12 from a flute14 in the body 4. Also conceivable and equally suitable are not depictedconfigurations, in which the guide bevel 10 follows the outer surface 12or divides said surface into multiple partial outer surfaces in thedirection of rotation U.

The guide bevel 10 further also comprises a so-called secondary cuttingedge 16, which precedes in the direction of rotation U and thus forms aleading edge of the guide bevel 10.

In the present case, the guide bevel 10 has an end section 18 toward thefront side F, which is tapered. In other words: The guide bevel 10extends toward the front side F and, in this direction, ends in an endsection 18 which is tapered in relation to the rest of the guide bevel10. The end section 18 forms an end of the guide bevel 10, so that ithas a reduced bevel width 20 on the end and toward the front side F,wherein the bevel width 20 is measured perpendicular to guide bevel 10.Such a guide bevel 10 with a tapered end section 18 is particularlyuseful for a drill 2 having a body 4 which tapers toward the rear sideR, i.e. which has a so-called “taper”, as can be seen in the drill 2 inFIG. 5 , for example. Such a body 4 is usually slightly cone-shaped, sothat its diameter on the front side F is 1% to 5% larger, for example.However, a tapered end section 18 is furthermore also advantageous forother drills 2.

In the present case, the end section 18 is tapered as a result of theformation of a free surface 22 on the side of the body 4 along the guidebevel 10. Said free surface is disposed on the side of the body 4 andreplaces a part of the guide bevel 10, so that it is narrower toward itsend. This can be seen particularly clearly in FIGS. 1, 3, 5 and 8 . Thefree surface 22 is set back in radial direction R in relation to theguide bevel 10. On the end section 18, the free surface 22 and the guidebevel 10 extend directly next to one another in axial direction A andare thus directly adjacent to one another. The free surface 22 nowdistinguishes itself from the guide bevel 10 in that the drill 2 has asmaller diameter D on the free surface 22. During operation, only theguide bevel 10 is in contact with the inner wall of the bore, but notthe free surface 22, so that the contact surface of the drill 2 to thebore along the end section 18 is reduced.

The free surface 22 is similar to the outer surface 12, in that the freesurface 22 is likewise set back in radial direction R relative to theguide bevel 10. At least on the side of the body 4, however, the freesurface 22 is significantly smaller than the outer surface 12. The freesurface 22 is also separate from the outer surface 12 and is not a partof said outer surface, but it does adjoin the outer surface 12. Whereasthe outer surface 12 typically extends along the entire guide bevel 10,the free surface 22 extends in axial direction A only along the endsection 18, and therefore does not reach the rear side B of the drill 2.The outer surface 12 is furthermore typically configured with a constantradius, whereas the free surface 22 does not necessarily have a constantradius, but rather deviates from that. In addition, the free surface 22protrudes in radial direction R relative to the outer surface 12 and istherefore located between the guide bevel 10 and the outer surface 12with respect to the radius.

In the design examples shown, the free surface 22 directly follows theend section 18 in the direction of rotation U. The guide bevel 10 andits secondary cutting edge 16, thus precede the free surface 22, so thatthe end section 18, which follows in the direction of rotation U,transitions into the free surface 22 which then slopes away in radialdirection R and thus results in a reduced diameter D of the body 4behind the guide bevel 10. Lastly, following in the direction ofrotation U, the outer surface 12 then adjoins the free surface 22. Inthe two configurations shown, a step 24 is formed between the freesurface 22 and the outer surface 12; in another not depictedconfiguration, in contrast, the free surface 22 transitions to the outersurface 12 without edges. In the design examples shown, the free surface22 transitions into the guide bevel 10 without steps, i.e. withoutedges, as well. There is then no step or edge at the transition betweenthe guide bevel 10 and the free surface 22; instead the transition as awhole is continuous and rounded.

In the design examples shown here, the free surface 22 comprises twopartial surfaces 26, 28, namely an axial surface 28 which extends on theside of the body 4 along the end section 18, and a radial surface 26which extends on the front side F, such that the free surface 22 as awhole is curved, namely from one side of the body 4 toward the frontside F. The boundary between the axial surface 28 and the radial surface26 is indicated in FIGS. 5 and 8 with a dashed line. This results in afurther difference between the outer surface 12 and the free surface 22,such that the outer surface 12 extends in axial direction A only up to acircumferential edge 30, thus ending at the tool tip 6, whereas the freesurface 22 is inserted into the tool tip 6 from the side of the body 4and beyond the circumferential edge 30. The two partial surfaces 26, 28are both configured without edges here and also transition into oneanother without edges, so that the free surface 22 is a curved surfacethat is entirely without edges. The tapered end section 18 is formed onthe side of the body 4 by the axial surface 28. The radial surface 26,on the other hand, is disposed on the front side F, generally points inaxial direction A, and forms a part of the tool tip 6.

In the embodiments shown, the radial surface 26 extends along the maincutting edge 8. The radial surface 26 furthermore follows the maincutting edge 8 in the direction of rotation U, is directly adjacent tosaid main cutting edge and thus also determines a clearance angle of themain cutting edge 8. In the design examples shown, the free surface 22is a first free surface that extends inward only along an outer part ofthe main cutting edge 8 and to the inside adjoins a second free surface32, which extends along an inner part of the main cutting edge 8 andinto the center. The first free surface 22 is also referred to as theouter free surface, whereas the second free surface 32 is referred to asthe inner free surface. The transition between the first and the secondfree surface 22, 32 is continuous here, i.e. there is no edge betweenthe two free surfaces 22, 32, so that the two free surfaces 22, 32together are also regarded as a single free surface 22. To the inside,the free surface 22 extends to an inner end of the main cutting edge 8.In the present case, the inner end of the main cutting edge 8 adjoins achisel edge 34, which extends in the center of the drill 2 and is formedby a point thinning 36 that, to the inside, directly adjoins the freesurface 22 here.

The main cutting edge 8 and the guide bevel 10, more specifically theirend section 18, end together in a cutting corner 38 that is adjoined bythe free surface 22 which follows in the direction of rotation U. Thecutting corner 38 thus forms a respective end point for the main cuttingedge 8 and the secondary cutting edge 16. As a matter of principle, animaginary boundary line G between the guide bevel 10 and the freesurface 22 also ends in the cutting corner 38. Overall, due to thetapered configuration, the guide bevel 10 tapers in the direction towardthe cutting corner 38 and ends there. The cutting corner 38 itself isentirely surrounded by the guide bevel 10, the free surface 22, and alsoby the flute 14.

In the design examples shown, the free surface 22 is configured entirelywithout edges. A configuration is generally conceivable, in which theouter surface 12 and the radial surface 26 are separated by acircumferential edge 30 that extends in the direction of rotation Uaround the longitudinal axis L and ends in the cutting corner 38. Due tothe specific free surface 22, however, the circumferential edge 30 endsprematurely in the present case and does not reach the cutting corner38. In fact, the free surface 22 separates the cutting corner 38 from anend of the circumferential edge 30 and lies in between, so that arounded and edge-free transition from the front side F to the side ofthe body 4 is realized in the direction of rotation U behind the cuttingcorner 38. The free surface 22 can thus be prepared in a single pass andin a single process step. Proceeding from a semi-finished product havinga circumferential edge 30 that extends to the cutting corner 38, thecircumferential edge 30 directly behind the cutting corner 38 is roundedby the free surface 22 and, as a result, the cutting corner is movedtoward the rear side B.

As already indicated, the guide bevel 10 has a bevel width 20 which, inthe present case, varies due to the tapered end section 18 along theguide bevel 10, i.e. is smaller on the end section 18. In the presentcase, the bevel width 20 outside the end section 18 corresponds to anormal width and, along the end section 18, the free surface 22 has awidth 40 that together with the bevel width 20 of the end section 18corresponds to the normal width. Taken together, the free surface 22 andthe end section 18 are thus just as wide as the rest of the guide bevel10. The bevel width 20 is also constant here along the guide bevel 10and outside the end section 18, so that the guide bevel 10 has thenormal width throughout, all the way to the end section 18, and thebevel width 20 then deviates from the normal width only along the endsection 18. In the design examples shown, the difference to the normalwidth is filled in by the free surface 22.

In the design examples shown and viewed from the side, the guide bevel10 is strip-shaped, the end section 18 in itself is strip-shaped aswell, and likewise also the free surface 22 along the end section 18.More specifically, in the design examples shown, the free surface 22 andthe end section 18 are approximately needle-shaped or funnel-shaped witha tapered section that is followed by a straight section of constantwidth 20, 40, which is then in turn followed by a further taperedsection that ends here in a point. The free surface 22, specifically itsaxial surface 28, and the end section 18 extend parallel to one another,so to speak, at least along the straight sections, so that the freesurface 22 and the guide bevel 10 quasi intertwine when viewed from theside. In other words: an imaginary dividing line between the end section18 and the free surface 22 extends parallel to the guide bevel 10, i.e.in the direction of said guide bevel. The width 40 of the free surface22 along the end section 18 is constant or decreasing in the directiontoward the rear side B, but not increasing. Conversely, the bevel width20 along the end section 18 in the direction toward the front side F islikewise constant or decreasing. Overall, therefore, the width 40 of thefree surface 22 and the bevel width 20 decrease monotonically toward therespective end.

FIG. 9 shows a variant of the drill 2, in which the end section 18 andthe free surface 22 are not parallel but are instead inclined relativeto one another, so that an imaginary dividing line between the endsection 18 and the free surface 22 is correspondingly inclined.

In the present case, the width 40 of the free surface 22 along the endsection 18 is between 20% and 60% of the bevel width 20 of the guidebevel 10 along the end section 18. The width 40 and the bevel width 20are measured on a respective straight section as described above. Theabsolute width 40 and the absolute bevel width 20 depend on the specificconfiguration and dimensioning of the drill 2.

In the design examples shown, the end section 18 is significantlyshorter than the entire guide bevel 10 and thus only forms a part ofsaid guide bevel. Specifically, in the present case, the end section 18has a length 42 that corresponds to 4% to 40% of a diameter D of thedrill 2, whereby the length 42 is measured along the guide bevel 10 andthe diameter D is a maximum diameter D of the drill 2.

To produce the drill 2, the end section 18 is tapered by grinding theend of the guide bevel 10. In the present case, this is done using a notdepicted grinding wheel. In the embodiments shown, the end section 18was tapered by grinding off a part of the guide bevel 10 by grinding ina free surface 22, which extends continuously from the front side F ofthe body 4 to a side of the body 4. Proceeding from a semi-finishedproduct having a guide bevel 10 with a continuously constant bevel width20, the end of the guide bevel 10 is partially removed and, as a result,the free surface 22 is formed.

The invention claimed is:
 1. A drill, comprising: a body extending alonga longitudinal axis (L) from a rear side (B) to a front side (F),wherein the body comprises a main cutting edge on the front side (F),wherein the body comprises a guide bevel, which extends in an axialdirection (A) toward the front side (F) along a secondary cutting edge,wherein, toward the front side (F), the guide bevel has an end sectionwhich is tapered as a result of a first free surface directly adjacentthe guide bevel in the axial direction (A), wherein the drill has asmaller diameter (D) on the first free surface than on the guide bevel,and wherein the body comprises a second free surface extending from thefirst free surface radially inward along the main cutting edge to achisel edge, wherein the body further comprises a cutting corner formingan end point for the main cutting edge and the secondary cutting edge,wherein the first free surface comprises two partial surfaces, namely anaxial surface, which extends on a side of the body along the endsection, and a radial surface, which extends on the front side (F) suchthat the first free surface as a whole is curved, wherein the radialsurface extends along the main cutting edge and follows the main cuttingedge in a direction of rotation (U), and wherein the axial surface ofthe first free surface has a width that is constant such that animaginary boundary line (G) between the guide bevel and the first freesurface extends parallel to the guide bevel.
 2. The drill according toclaim 1, wherein the first free surface follows the end section in adirection of rotation (U).
 3. The drill according to claim 1, whereinthe transition of the first free surface into the guide bevel is withoutsteps.
 4. The drill according to claim 1, wherein the first free surfaceis configured entirely without edges.
 5. The drill according to claim 1,wherein the guide bevel has a bevel width which, outside the endsection, corresponds to a normal width, and wherein, along the endsection, the first free surface has a width that together with a bevelwidth of the end section corresponds to the normal width.
 6. The drillaccording to claim 1, wherein, along the end section, the first freesurface has a width that is between 20% and 60% of a bevel width of theguide bevel along the end section.
 7. The drill according to claim 1,wherein the end section has a length which corresponds to 4% to 40% of adiameter (D) of the drill.